Your step length can be set in your Pacer's settings. If you have not set your step length, Pacer estimates your step length to be 0.4 x your height. If you have not set your height either, Pacer assumes an average height of 165cm.

For iPhone 5s and above:

These devices have built-in motion sensors that use your activity and location data to calculate the distance traveled. There is no need to set your step length on these devices.

You can also check the following setting to ensure accuracy for the distance data: